After playing a victim in the Season 1 episode "Russian Love Poem," she was cast in the current Season 12 as Assistant District Attorney Gillian "Jill" Hardwicke. Wednesday marks Sagemiller's second episode with this role.

Not only do Sagemiller and Mariska Hargitay have a past from previously working together, but so do their characters, Hardwicke and Detective Olivia Benson.

"There's something in my past, a personal connection that we have, something that she did for me and a family member who she helped out ... She's not aware of it yet [but] it becomes revealed in the next several episodes," the 36-year-old Sagemiller says.

While Hardwicke's background has yet to come to light, her personality, Sagemiller says, is front and center. "She's tough ... she has a heart, she just gets what she wants."

Sagemiller adds: "She sticks to the letter of the law, sometimes to a fault, but in the end I think she always does the right thing."

Watch this behind-the-scenes video with special guest star Maria Bello: